This invention relates to a driving system for a display in which X electrodes and Y electrodes are arranged in a matrix configuration, and for treating display information such as that relating to character, numeral or configuration in a time sharing manner.
It is necessary that the electronic circuit of a multi-functional electronic timepiece dynamically processes the display information which is stored in a shift register, in order to decrease the number of circuit elements and for the simplification of these elements. Additionally, the interface between a shift register and a driving circuit has many problems for producing a dot matrix display.
FIG. 1 shows a conventional dynamic logic circuit for an electronic timepiece in which the oscillating signal produced by oscillating circuit 1 is divided by dividing circuit 2 and the divided signal is provided to adder 3 and then to the shift registers 4 and 5. The divided signal cycles in the adder 3 and the shift registers 4 and 5 which act to count time. The shift register 4 consists of 4 bits and the serial signals of 4 bits are provided to the decoder 6 in parallel so as to be converted to display signals. The converted display information is taken out at every 4 bits and is stored in shift register 7. The output signal of the shift register 7 is applied to driving circuit 8 and the driving signal of the driving circuit 8 drives liquid crystal display 9. As mentioned above, in the case where the liquid crystal display is activated in the conventional manner, the transfer time of the Y electrode display signal is required for a predetermined time during which the shift register 7 stores the display information of all digits, because the 4 bits of information signal of the shift register 4 is converted into the display signals by the decoder 6 and the display signals are stored in the shift register 7 in turn, at the scanning time selecting one of the X electrodes.
Accordingly, the driving voltage of the X electrode cannot be synchronized with the driving voltage of the Y electrode. The display 9 is effected through the driving circuit 8 by a transfer pulse which transfers the display information to the shift register 7. From the above, the quality of the display becomes bad in view of the contrast and the cross-talk phenomenon. It is disadvantageous that the consumption of the current is great in the liquid crystal display since the transfer pulse is transferred with a considerable high frequency. It has been proposed that the driving system for the liquid crystal display store the display signals of all the digits in a memory circuit after the display signals are filled in the shift register and that it make the driving voltage scanning the X electrodes synchronous with the driving voltage scanning the Y electrodes, so that it needs double memories in order to eliminate the effect of the transfer pulse and the variation of effective voltage depending on the non-synchronization. However, in such a system, the number of circuit elements are increased, since double memories are required.